Exposure problems (x100)

I've gotten my x100 for about a month now, and I'm generally very pleased with the image quality of the camera. In the last week, I've noticed that my camera seems to measure the exposure wrongly (in all 3 different metering modes) for apertures values higher than f2.0 (shooting in aperture priority).

For example, at f2.0, the shot turns out perfectly exposed, while from f4.0 onwards, all my pictures are increasingly overexposed, with iso and the subject held constant. I've noticed that the shutter speed calculation seems to be fairly linear; shooting the same object at f2.0, the camera decides it needs a shutter speed of 1/250, and at 2.8, a speed of 1/125, f4.0 at 1/62 and so on.

1. Apparently the camera measures the amount of light entering the aperture at f2.0 and sets a shutter speed, and any changes to the aperture is linearly affecting the resultant shutter speed, which results in overexposure for most of my photos.

2. The reason I only realized the above in the last week was that I was shooting mainly in manual mode, and ignored the ev meters. As it stands, to get a similarly exposed picture of the same subject as at f2.0, the camera measures the exposure values to be as such:

at f4.0 - 1 and a third stops underexposed
at 5.6 - 1 and a third stops underexposed
at f.8.0 - 1 and 2 thirds stops underexposed

at f11 and f16 - 2 stops underexposed, and I normally have to play around with the shutter speed to get the exposure for f16 correct.

As a result, I pretty much can't shoot in aperture priority with an aperture value higher than f2.0 without getting my pictures overexposed.

I'm slightly reluctant to send it in to Fujifilm Singapore for checking as they've informed me that the check alone will take about 1-2 weeks, and while the meters and program modes are screwy, I can still get proper pictures shooting in full manual and ignoring the meters.

My question is, Is this normal? Firmware or hardware problem? I'm thinking that my set is a lemon, and would like to get opinions from the forumers here. Thanks in advance!